1. Field of Invention
The present invention relates to a resin-molded electronic component, and to a method of producing such a resin-molded electronic component.
2. Description of Related Art
In recent years, great reductions in the size and thickness have been achieved for various small-sized information devices, such as an HDD (hard disk drive), a mobile computer, and an IC card, and also for various mobile communication devices, such as a portable telephone, a mobile telephone, and a paging system. Correspondingly, enhancements in performance have been achieved for various electronic components, such as a piezoelectric resonator and a piezoelectric oscillator for use in information devices or communication devices, wherein, in many cases, these electronic components are produced into forms suitable for automatic mounting.
For example, in the case of a piezoelectric resonator of such electronic components, a quartz resonator chip serving as a piezoelectric material in the form of a very thin plate is disposed in a package. Such a quartz resonator chip includes metal electrode films formed in particular patterns and disposed on two opposite surfaces of the quartz plate. If a driving voltage is applied between the two electrode films, the quartz resonator chip vibrates at a specific vibration frequency depending upon the thickness of the quartz resonator chip. The vibration is converted into an electrical signal and used, as a clock signal, in a device in which the quartz resonator is disposed.
In such piezoelectric resonators, if a package in which a piezoelectric resonator chip is housed has a special shape, or if electrode terminals which are to be connected to a mounting board are formed at locations different from those of other types of electronic components, it is impossible to automatically mount piezoelectric resonators. To avoid the above problem, it is known to produce a molded component such that a package is molded with resin and electrode terminals are formed using lead frames so that the resultant molded component has a form suitable for automatic mounting using an automatic mounting machine.
When a piezoelectric resonator is produced into a molded form according to the conventional technique, electrode terminals must be formed so as to adapt to the external shape of a resin-molded part.
More specifically, in the case where an electronic component is produced in a resin-molded form, terminals must be formed so as to extend outwardly from a resin-molded part at locations precisely corresponding to lands of a conductive pattern formed on a mounting board.
To this end, before performing molding, an electronic component is precisely positioned with respect to a lead frame for forming a terminal (terminal-forming lead frame), and then lead terminals of the electronic component are connected to the terminal-forming lead frame. Thereafter, the electronic component connected with the lead frame is placed in a mold, and a molding material is injected into the mold thereby performing molding.
However, in many cases, electronic components, such as a piezoelectric resonator, are very small in size, and thus it is difficult to precisely position lead terminals of electronic components with respect to the terminal-forming lead frames. If the positioning is not precise enough, a good connection between lead terminals and a lead frame is not achieved, and thus a resultant product has degraded performance.
Furthermore, if an electronic component is not placed at a correct position in a mold, a problem not only occurs in forming electrode terminals, but also a problem occurs that the electronic component is not properly covered with a molding material and the electronic component is partially exposed from a resin-molded part.
The conventional molded component has another problem as described below.
FIG. 39 illustrates one production step of a conventional molded component. In this production method, an electronic component to be molded, that is, a piezoelectric resonator chip housed in a cylindrical package 511, is inserted between lead frames 513 and 514 disposed on a terminal-forming frame 521 and is properly positioned.
As shown in FIG. 39, the lead frame 513 formed on one end of the terminal-forming frame 521, which will become an electrode terminal of the molded component, includes a part 513a extending substantially horizontally from the terminal-forming frame 521, a rising-up part 513b formed integrally with the horizontal part 513a and extending substantially vertically from the inner end of the horizontal part 513a, and a lead terminal connection part 513c extending horizontally from the upper end of the rising-up part 513b. 
On the other hand, a lead frame 514 formed on the other end of the terminal-forming frame 521 includes a rising-up part 514b formed on the inner end of the lead frame 514 and an outwardly extending part 514a which is integrally formed with the rising-up part 514b and which is connected to the terminal-forming frame 521. After completion of a resin-molding process, an end portion of the outwardly extending part 514a becomes a horizontal part extending horizontally from a resin-molded part and serving as a dummy terminal.
After inserting the packaged electronic component 511 between the lead frames 513 and 514 located on the two respective ends, the outer lead 512b of the package 511 and the connection part of the lead frame 513 are welded to each other, as shown in an enlarged fragmentary view of FIG. 40, by applying a voltage between an upper electrode 532 and a lower electrode 531 of an electrode block (not shown in FIG. 40).
In the above process, the outer lead 512b is put on the lead frame 513, and the lower electrode 531 is brought from below into contact with the lead frame 513, and the upper electrode 532 is brought from above into contact with the outer lead 512b. Thereafter, the voltage is applied between the upper electrode 532 and the lower electrode 531 while pressing the lead frame 513 and the outer lead 512b between the upper electrode 532 and the lower electrode 531.
However, because the lead terminal connection part 513c extends substantially vertically from the rising-up part 513b of the lead frame 513, a gap 513e is created when the lower electrode 531 comes into contact with a corner 513d at which the lead frame 513 is bent. If such a gap 513e is created, an applied current cannot flow sufficiently, and thus welding is not well performed.
After completion of the welding described above, the package 511 is sandwiched between an upper mold 534 and a lower mold 533 and a molding material is injected so as to mold the package 511 by transfer molding, as shown in FIG. 41. In this molding process, if horizontally extending parts of the lead frames 513a and 514a are slightly inclined upwardly in an inward direction, a gap 533a or 533b is created.
The creation of the gap 533a or 533b can cause a molding material to intrude into the gap 533a or 533b, and thus can cause a burr to be created on a surface serving as a mounting surface, which is to be contacted with a surface of a mounting board when being mounted, of the molded component. The burrs can result in an insufficient mounting strength when the molded component is mounted on the board, and thus can cause degradation of quality.
The conventional molded component has still another problem as described below.
FIG. 42(A) illustrates a process of producing a resin-molded part 515 by molding a package 511 with resin using a terminal-forming frame 521. A gate 535 for use in molding is formed near a dummy-terminal lead frame 514.
The lead frame 514 is formed integrally with the terminal-forming frame 521 made of metal such as a copper-based alloy.
More specifically, the terminal-forming frame 521 has a space 521a in the form of a rectangular window, which is larger than the size of the electronic component, and which is surrounded by a peripheral part 521b. In this space 521a, the above-described electronic component, such as a piezoelectric resonator chip, is placed between the above-described lead frame 514 and a lead frame (not shown) on the opposite end, and a resin-molded part 515 is produced using a molding material. Through the above process, a molded component 500 is obtained.
In the case where the electronic component is a piezoelectric resonator chip or a similar device, lead terminals are disposed on only one side. In this case, electrode terminals used to mount the molded component 500 are formed as follows. That is, the lead frame on the opposite end, which is not shown in FIGS. 42(A) and 42(B), is electrically connected to the lead terminal of the electronic component in the resin-molded part 515 so that the lead frame will become an electrode terminal. On the other hand, the lead frame 514, shown in FIGS. 42(A) and 43(B), will become a dummy terminal which will be used only to fix the molded component 500 on a board when the molded component 500 is mounted on the board.
In this case, the lead frame 514 is placed at a height substantially equal to the lower surface of the resin-molded part 515, and the horizontal part 514a in the form of a flat plate is exposed to the exterior of the resin-molded part 515. As shown in FIG. 42(B) which is a cross-sectional view taken along plane fxe2x80x94f of FIG. 42(A), the gate 535 interferes with the horizontal part 514a, in the form of the flat plate, of the lead frame 514, and thus, the gate 535 is formed at a height shifted upward by an amount equal to the thickness t of the horizontal part 514a. As a result, the distance between the upper end of the gate 513 and the upper end of the resin-molded part 515 is reduced to a small value denoted by xe2x80x9caxe2x80x9d.
The size of the piezoelectric resonator 500 is very small. For example, the total thickness of the resin-molded part 515 shown in FIG. 42(A) is about 1.3 mm. Thus, if the thickness from the upper end of the gate 535 shown in FIG. 42(B) to the upper end of the resin-molded part is as small as xe2x80x9caxe2x80x9d, there is a possibility that a crack is created in this portion when the gate is cut off. Such a crack results in degradation in the quality of the product.
The conventional molded component has still another problem which occurs during the molding process, as described below.
In the conventional molding process, as shown in FIG. 42, the packaged electronic component placed in the space 521a of the terminal-forming frame 521 is molded with a molding material, and thus the resin-molded part 515 is formed.
In this molding process, the peripheral part 521b of the terminal-forming frame 521 is placed between an upper mold 534 and a lower mold 533, as shown in FIG. 43. More specifically, as shown in FIG. 44, which is a cross-sectional view taken along plane dxe2x80x94d of FIG. 43, the package 511 is tightly held between a contact part 533a formed on the upper surface of the lower mold 533 and an eject pin 534a which can move up and down in the inside of the upper mold 534, and a molding material is injected into the mold so as to form the piezoelectric resonator 500 including the resin-molded part 515, as shown in FIG. 45.
The width of the molding resin of the resin-molded part 515 is denoted by xe2x80x9ccxe2x80x9d in FIG. 45. However, because the peripheral part 521b of the terminal-forming frame 521 is sandwiched between the upper mold 534 and the lower mold 533 as described above with reference to FIG. 44, burrs 515a and 515a are created in gaps between the upper mold 534 and the lower mold 533. This results in an unwanted increase in the total external size of the obtained piezoelectric resonator 500, as denoted by xe2x80x9cbxe2x80x9d in FIG. 45.
A first object of the present invention is to provide a molded component and a production method thereof, in which an electronic component is precisely positioned with respect to a terminal-forming lead frame, thereby ensuring that a good electrical connection is achieved and the electronic component is properly molded with resin, thereby forming a resin-molded part.
A second object of the present invention is to provide a method of producing a molded component, in which an electronic component is precisely positioned with respect to a terminal-forming lead frame, thereby ensuring that a good electrical connection is achieved and molding is performed without creating burrs on a mounting surface of a resultant molded component, thereby ensuring that a strong mounting connection is achieved.
A third object of the present invention is to provide a molded component and a production method thereof, in which a crack is prevented from being created when a gate is cut off after producing a resin-molded part using a molding material.
A fourth object of the present invention is to provide a resin-molded structure of a molded component and a method of producing such a structure, in which no burrs are created on a side face during the step of molding an electronic component, having a shape which is long in one direction, with a molding material, and thus a small resin-molded structure can be realized.
According to an aspect of the present invention, to achieve the first object described above, there is provided a molded component obtained by inserting an electronic component between lead frames disposed at two respective ends and then molding the electronic component with resin. In this molded component, at least a lead frame disposed on one end serves as an electrode terminal exposed from a resin-molded part and the lead frame on the other end serves as a dummy terminal. The dummy terminal includes a horizontal part having an end portion exposed to the exterior of the device and extending horizontally from the resin-molded part, and a rising-up part which is formed integrally with the horizontal part and which rises up from the inner end of the horizontal part. The angle between the rising-up part and the horizontal part is set to be slightly smaller than 90xc2x0.
In the molded component according to the present invention, two types of lead frames are provided, one of which is used to form the electrode terminal, and the other one is used to form the dummy terminal, which includes the horizontal part having an end portion exposed to the outside from the resin-molded part, and the rising-up part, which is located on the inner side of the horizontal part, that is, at a side of an end of the electronic component inserted between the two frames and which is formed integrally with the horizontal part such that the rising-up part rises up from the inner end of the horizontal part. The angle between the rising-up part and the horizontal part is set to be slightly smaller than 90xc2x0. Because the angle is set in the above-described manner, the rising-up part is inclined outwardly, that is, inclined apart from the electronic component. Therefore, when the electronic component is inserted from above into a space between the lead frames disposed on the two respective ends, the electronic component is guided by the outwardly-inclined surfaces, and thus the electronic component is precisely positioned without encountering interference between an edge of the rising-up part and an edge of the electronic component.
The first object described above is also achieved by a method of producing a molded component according to the present invention. In this method, a molded component is obtained by inserting an electronic component between lead frames disposed at two respective ends and then molding the electronic component with resin. The method includes the step of connecting a lead terminal to an electrode terminal by bringing the lead terminal of the electronic component into contact with at least one of lead frames disposed on the two respective ends, and then applying a voltage thereto so as to connect the lead terminal to the electrode terminal. The connection step includes the steps of positioning the lead frame with respect to an electrode block that supplies the voltage; and bringing the electronic component into contact with an electronic component holding device formed on the electrode block, thereby correctly positioning the lead terminal of the electronic component with respect to the one of lead frames disposed on the two respective ends.
In the method according to the present invention, the lead frame is positioned with respect to the electrode block that supplies the voltage, and the electronic component is brought into contact with the electronic component holding device formed on the electrode block, thereby ensuring that the electronic component, the lead frames, and the electrode block are all precisely positioned with respect to one another. This makes it possible to precisely position the lead terminal of the electronic component with respect to at least one of lead frames, and thus it becomes possible to properly connect the lead terminal to that lead frame. This ensures that a good electrical connection is achieved.
The first object described above is also achieved by a method of producing a molded component according to another aspect of the present invention. In this method, a molded component is obtained by inserting an electronic component between lead frames disposed at two respective ends and then molding the electronic component with resin. The method includes the step of molding the electronic component with resin after connecting a lead terminal to an electrode terminal by bringing the lead terminal of the electronic component into contact with at least one of lead frames disposed on the two respective ends, and then applying a voltage thereto so as to connect the lead terminal to the electrode terminal. A positioning device, having a contact surface which fits with the external shape of the electronic component, is disposed in a mold used in the molding step. Molding is performed while maintaining the positioning device in contact with the electronic component.
In the method according to the present invention, positioning of the lead terminal of the electronic component is not performed on the electronic component, and instead is performed in the mold, such that the positioning device, having a contact surface which fits with the external shape of the electronic component, is disposed in the mold used in the molding step, and molding is performed while maintaining the positioning device in contact with the electronic component. In this method, because the electronic component is fit with the contact surface of the positioning device in the mold and held by the positioning device, the electronic component does not deviate in a lateral direction, and thus the resultant molded electronic component does not have a part exposed from a side of the resin-molded part.
The first object described above is also achieved by another aspect of the invention, in which the positioning device includes a recessed part formed in the contact surface which fits with the electronic component, and molding is performed such that the recessed part is filled with the molding material.
In the invention, because the contact surface of the positioning device is formed so as to fit with the external shape of the electronic component, the molding material cannot easily enter between the electronic component and the contact surface during the molding process. To avoid the above problem, the recessed part is formed in the contact surface so that the molding material can enter into the recessed part, thereby ensuring that the side, in contact with the positioning device, of the electronic component is also covered with the molding material and thus the electronic component is entirely molded with resin.
The second object described above is achieved by a method of producing a molded component according to another aspect of the present invention. In this method, a molded component is obtained by inserting an electronic component between lead frames disposed at two respective ends, and then molding the electronic component with resin. A lead frame, disposed on one of the two ends of the electronic component, includes an outwardly extending part, a rising-up part which rises up from the inner end of the outwardly extending part, and a lead terminal connection part extending inwardly from the end of the rising-up part. The method includes the steps of, before molding the electronic component with resin, disposing the lead frame on one end, such that the lead terminal connection part thereof is slightly inclined downwardly in an inward direction; and thereafter, bringing an electrode that applies a welding voltage into contact with the lead terminal connection part from below, and then placing a lead terminal of the electronic component upon the lead terminal connection part, and finally connecting the lead terminal to the lead terminal connection part.
In the method according to the present invention, in a state in which one lead frame, which will become the electrode terminal is attached to the terminal-forming frame, at least the lead terminal connection part of the lead frame is inclined downwardly in the inward direction. Herein, the xe2x80x9cinward directionxe2x80x9d refers to a direction toward the electronic component.
In such a state, the lead of the electronic component is placed upon the lead terminal connection part of the terminal-forming frame, and they are sandwiched between a lower electrode and an upper electrode and a voltage is applied thereto to weld them to each other. During the above process, the lower electrode is brought from below into contact with a lower edge of the lead terminal connection part in the slightly inclined position, and the lead terminal connection part is pushed up by the lower electrode. As a result, the lead terminal connection part is changed into a horizontal position. Thus, the upper surface of the lower electrode and the lower surface of the lead terminal connection part extending horizontally are entirely in contact with each other without creating a gap between them, and thus the voltage can be properly applied thereto. This ensures that they are connected to each other in a highly reliable fashion.
In the molding process performed after completion of connection of the lead terminal, the electronic component is sandwiched between an upper mold and a lower mold. At this stage, the outwardly extending part is slightly inclined downward because the outwardly extending part is substantially parallel to the lead terminal connection part. However, when the lead terminal connection part is moved into a horizontal position, the outwardly extending part is also moved into a horizontal position, and thus no gap is created between the lower mold and the outwardly extending part. Therefore, no burrs are created on the lower surface of the molded component. The lower surface of the molded component is brought into contact with a surface of a board when the molded component is mounted thereon. Thus, the lower surface of the molded component can be directly contacted with a land formed on the board without any burrs. As a result, an enhancement in the strength of the mounting connection is achieved.
The second object described above is also achieved by another aspect of the invention. According to the invention, a lead frame disposed on the other one of the two ends of the electronic component includes an end part extending outwardly and a rising-up part, which is formed integrally with the outwardly extending part, and which rises up from the inner end of the outwardly extending part, and, before molding the electronic component with resin, the lead frame is disposed such that the outwardly extending part is slightly inclined downwardly in an inward direction.
In the invention, unlike the method previously described, because the other lead frame is not connected to the lead terminal, the other lead frame is not changed by the lower electrode. However, in the molding process, although the outwardly extending part of the other lead frame is slightly inclined downward in the inward direction, this outwardly extending part placed between the upper mold and the lower mold is pushed up by the lower mold, and thus the outwardly extending part is brought into a horizontal position. Therefore, no gap is created between the lower mold and the lead frame. Therefore, no burrs are created on the lower surface of the molded component. The lower surface of the molded component is brought into contact with a surface of a board when the molded component is mounted thereon. Thus, the lower surface of the molded component can be directly contacted with a land formed on the board without any burrs. As a result, an enhancement in the strength of mounting connection is achieved.
According to another aspect the present invention, a groove is formed in a surface, which is to be used as a contact surface when the molded component is mounted, of the lead frame disposed on one of the two ends, and the lead frame including the grooved part is plated with solder.
In the invention, because at least one of lead frames exposed from the resin-molded part of the molded component (the lead frame which becomes the electrode terminal) has a groove formed in a surface which is to be contacted with a board when being mounted, and because the grooved portion is also plated with solder, when the molded component is mounted on the board, the grooved surface, which is slightly away from the contact surface of the board, can also be wet with connection solder. Thus, the strength of mounting connection is enhanced, and an electrical connection is made in a more reliable fashion.
The third object described above is achieved by a molded component according to another aspect of the present invention. According to the invention, the molded component is obtained by inserting an electronic component between lead frames disposed at two respective ends, and then molding the electronic component with resin. The molded component is provided such that at least a lead frame disposed on one end serves as an electrode terminal exposed from a resin-molded part, and the lead frame on the other end serves as a dummy terminal. The dummy terminal includes a horizontal part having an end portion exposed to the exterior and extending horizontally from a part near a lower edge of the resin-molded part, and at least a part, exposed to the exterior from the resin-molded part, of the horizontal part is divided into two portions along a horizontal direction.
In the molded component according to the present invention, the part, exposed to the exterior from the resin-molded part, of the dummy terminal is divided into two portions along the horizontal direction. This allows a gate used for injection of a molding material to be formed in the mold, in a region between the two divided portions of the dummy terminal. Because no lead frame is present in the region between the divided portions of the dummy electrode, the gate can be formed at a lower height. That is, the location of the gate can be lowered by a value corresponding to the thickness of the lead frame. As a result, in the molded component having a very small size, the distance from the top of the gate to the top of the resin-molded part can be large enough to prevent a crack from being created in this upper part of the resin-molded part when the gate is cut off.
The third object described above is also achieved by a method of producing a molded component according to another aspect of the present invention. In this method, a molded component is obtained by inserting an electronic component between lead frames disposed at two respective ends, and then molding the electronic component with resin. The method is performed such that at least a lead frame disposed on one end serves as an electrode terminal exposed from a resin-molded part and the lead frame on the other end serves as a dummy terminal. The dummy terminal includes a horizontal part having an end portion exposed to the exterior and extending horizontally from a part near a lower edge of the resin-molded part. At least a part, exposed to the outside from the resin-molded part, of the horizontal part is divided into two portions along a horizontal direction. In the resin molding step, a gate for passing a molding material is formed in a region between the two divided portions of the dummy terminal.
In the method according to the present invention, as in the aspect of the invention discussed above, the part, exposed to the outside from the resin-molded part, of the dummy terminal is divided into two portions along the horizontal direction. Thus, for the same reason as discussed above, if the gate used for injection of the molding material is formed in the region between the two divided portions of the dummy terminal, the distance from the top of the gate to the top of the resin-molded part can be large enough to prevent a crack from being created in this upper part of the resin-molded part when the gate is cut off.
The fourth object described above is achieved by a resin-molded structure of a molded component according to another aspect of the present invention. The resin-molded structure is obtained by inserting an electronic component between lead frames disposed at two respective ends, and then molding the electronic component with resin. The structure is provided such that the lead frames are disposed such that they project inwardly from a peripheral part formed so as to surround the electronic component, and a gap is formed between a side surface of the electronic component and the peripheral part in a state in which the electronic component is connected to the lead frames so that a mold used in the resin-molding process is allowed to enter into the gap.
In the resin-molded structure according to the present invention, the lead frames are disposed such that they project inwardly from the peripheral part formed so as to surround the electronic component, and a large gap is formed between a side surface of the electronic component and the peripheral part in a state in which the electronic component is connected to the lead frames so that the entire contact surface of the upper mold and the entire contact surface of the lower mold can be located within the gap between the peripheral part and the side of the electronic component. Thus, it becomes possible to prevent burrs from being created on a side of the electronic component which would otherwise be created due to imperfect contact between the facing surfaces of the upper and lower molds. This allows a reduction in the total external size of the molded component.
The fourth object described above is also achieved by a method of producing a molded component according to another aspect of the present invention. In this method, a molded component is obtained by inserting an electronic component between lead frames disposed at two respective ends and then molding the electronic component with resin. The method is performed such that the resin molding step includes the steps of preparing a terminal-forming frame, including a peripheral part surrounding the electronic component, and also including the lead frames which are formed such that they project inwardly from the peripheral part. A gap is formed between a side surface of the electronic component and the peripheral part in a state in which the electronic component is connected to the lead frames so that a mold used in a resin-molding process is allowed to enter into the gap. The electronic component is molded after placing the mold such that contact surfaces of mold elements are located between the side surface of the electronic component and the peripheral part.
In the method according to the present invention, because the terminal-forming frame has the gap which is formed between a side surface of the electronic component and the peripheral part so that a mold used in a resin-molding process is allowed to enter into the gap, the entire contact surface of the upper mold, and the entire contact surface of the lower mold, can be located within the gap between the peripheral part and the side of the electronic component. Thus, for the same reason as previously discussed, it becomes possible to prevent burrs from being created on a side of the electronic component which would otherwise be created due to imperfect contact between the facing surfaces of the upper and lower molds. This allows a reduction in the total external size of the molded component.